I. Technical Field
The present invention relates to electronic security tour recording systems of the type used by a watchman in recording his attendance at specified tour stations. The invention also relates to coded data carriers and coded data readers which may be employed in such systems.
II. Discussion of the Prior Art
It is important in many industrial and commercial establishments that periodic security checks be conducted at different stations or locations within the establishment premises. In conducting such security checks, watchmen generally follow a pre-arranged tour or itinerary so that critical areas may be checked at prescribed times. It is important that a record be provided of the individual checks made by the watchmen, particularly for purposes of satisfying insurance company requirements, but also to permit supervisory personnel to assure that the appropriate security checks have been made.
Prior art electronic security tour recording systems are of two general types. The first type, as exemplified by U.S. Pat. No. 3,990,067 (Van Dusen et al) employs a portable key carried by the watchman who inserts the key into appropriate key readers at various tour stations. Station identification signals are transmitted from the visited tour stations via hard wire line, radio transmission, or the like, to a remote monitoring location at which the signals are processed. second type of electronic security tour recording system is typified by U.S. Pat. Nos. 3,922,649 (Thome) and 3,959,633 (Lawrence et al). These systems employ a code reader which is carried by the watchman to the various stations at which respective coded station keys are inserted into the reader. The reader stores the station key identification code, and in some cases the time of insertion, for subsequent read out of the stored information into a central computer. Hardcopy print out of station check data may be obtained from the central computer. Both types of systems described above require a central processor, or the like, in addition to the watchman's unit, to provide a hardcopy record of a tour.
It is also known in the prior art, as disclosed in the aforementioned Lawrence et al patent,to provide optical reading of an optically coded key located at each tour station. The Lawrence et al key takes the form of a rigid body member having a multiplicity of light transmitting holes defined therein. Insertion of the key into a portable reader actuates a similar multiplicity of light sources which transmit respective sensing beams across a space into which the key is inserted. Multiple sensors receive the respective beams, or not, depending upon the open and closed bit code of the holes in the key. This parallel sensing requires one light source for each code bit; thus, the system experiences considerable battery drain during code reading operations, a problem which is significant in a portable unit that must be used for one or more relatively long tours of the security stations. A need for frequent battery charging removes the watchman's unit from use for a considerable period of time. In addition, since each key code is clearly evident by its visible hole pattern, a watchman can readily fabricate a master key in which the holes can be selectively blocked or unblocked for use in making entries into the reader without actually touring the security stations.
The prior art discloses opto-electronic card readers using serially-arranged bits in a data carrier which are read in sequence as the carrier is inserted into a reader. An example of such a reader is found in U.S. Pat. No. 4,237,375 (Granholm). The coded data carrier in this reader is a laminated card member wherein the card field bits are hidden from view. If a data field is improperly formed during assembly, or if it becomes inoperative due to use or mis-use, the assembler or user is not aware of the problem unless and until the card is not read properly by the reader. Moreover, the inability of the user to see the data fields results in frequent improper orientation of the code carrier into the reader. Further, the Granholm patent discloses a data reading scheme wherein two spaced light beams are required to sense the data fields, the beams being mutually spaced to distinguish proper card insertion into the reader from insertions which are too slow. The insertion discrimination requires circuitry for analyzing the two pulse trains from the respective data beam sensors. It is desirable to eliminate the need for two data sensors, particularly where the beams must be critically spaced with respect to the data field spacing. Further, it is desirable to eliminate the need for comparing and analyzing two contemporaneous pulse trains for critical phase variations.
The aforementioned Lawrence et al patent recognizes that battery drain caused by the parallel data sensing beams can be minimized by emitting these beams only when a key is inserted into the reader. To this end, Lawrence et al provide two sensing light sources, in addition to the parallel data beam sources, which emit pulsed key detector beams. Interruption of the key detector beam pulses by a key results in energization of the data beams. It is desirable to eliminate the need for additional beam sources and detectors used expressly for detecting key presence.